Functions
2.15 Monitoring Functions
SIPROTEC, 7SD610, Manual
C53000-G1176-C145-6, Release date 02.2011
204
A wire break is signalled under the following conditions:
• A suspected local wire break has been detected.
• The logic for detecting the circuit breaker position (see Section 2.16.1, Detection of the Circuit Breaker Po-
sition) does not signal an open circuit breaker pole. Wire break detection is not possible if the circuit breaker
is open. If the breaker position cannot be determined, a closed circuit breaker is assumed.
• In all voltage channels, no jump must have been detected. Jumps in these channels indicate a genuine
power system fault.
• In the other current channels, there must have been no jump without wire break detection. Jumps in the other
current channels also suggest a power system fault, except if a suspected local wire break has been detect-
ed for the affected phases.
• The device at the other end of the protected object must not have signalled a jump. The jump information is
transferred together with the differential protection measurements, so that this information is available simul-
taneously with the first run of the differential protection after the jump.
• In the phase, also the devices at the other end of the protected object must not have measured a phase
current of more than 2 I
N
. A phase current of such a magnitude is a certain indicator of a power system fault.
A wire break detected by the aforementioned criteria is transmitted to the device at the other end of the pro-
tected object and immediately prompts a broken wire report. The differential protection function will also be
blocked provided that it has been configured accordingly.
In the event of a local wire break, the message „broken wire I
Lx
“ (no. 290, 291, 292) is generated, whereas
when the broken wire is detected at the other end of the protected object, the message is „broken wire at the
other end I
Lx
“ (no. 297, 298, 299). If the broken wire monitoring is deactivated, the message 295 „Broken
wire OFF“ ensues.
The broken wire monitoring is reset by the return of the phase current (I
Lx
> 0.05 I
N
) or by the binary input
message 3270 „>RESET BW“. In 1-1/2 circuit breaker arrangements, the function can only be reset by the
binary input message because the current magnitude is no reliable criterion for a reset of the broken wire mon-
itoring.
If the communication between the devices is disturbed, the device operates in emergency operation. The dif-
ferential protection is not active. The wire break detection then operates only with the locally available informa-
tion. Multipole wire break is not indicated in emergency operation.
It has to be observed that electronic test devices do not behave like a circuit breaker so that pickup can occur
during such tests.
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